Reduce stack manipulation (use M instead of A)

master
Nemo 3 years ago
parent b186ee7df1
commit be69ac321d
  1. 20
      projects/07/StackArithmetic/SimpleAdd/SimpleAdd.asm
  2. 49
      vm/VMTranslator.php

@ -4,10 +4,8 @@ D=A
@SP
A=M
M=D
A=A+1
D=A
@SP
M=D
M=M+1
// end push constant 7
// push constant 8
@8
@ -15,25 +13,17 @@ D=A
@SP
A=M
M=D
A=A+1
D=A
@SP
M=D
M=M+1
// end push constant 8
// ==== add ====
// pop starts
@SP
A=M
A=A-1
A=M-1
D=M
// pop ends
// inner add starts
A=A-1
D=D+M
// inner add ends
M=D
A=A+1
D=A
M=D+M
@SP
M=D
// ==== add ====
M=M-1

@ -68,50 +68,63 @@ class Parser {
class CodeWriter {
function __construct($outputFile) {
$this->ic = 0;
$this->file = fopen($outputFile, "w");
}
function __destruct() {
fclose($this->file);
}
function writeArithmetic(String $command ) {
// Read top of stack to D
$this->write([
"// ==== $command ====",
"// pop starts",
"@SP",
"A=M",
"A=A-1",
"A=M-1",
"D=M",
"// pop ends",
"// inner $command starts",
'A=A-1',
]);
switch ($command) {
case 'add':
// But add it to previous D this time
$this->write([
"// inner add starts",
"A=A-1",
"D=D+M",
"// inner add ends",
"M=D+M"
]);
break;
case 'eq':
$jumpPointer = $this->ic+5;
$this->write([
'D=M-D', // ic
'M=0', // set M=0, in case they aren't equal
"@{jumpPointer}",
'D;JEQ', //ic+2
'M=0', //ic+3
'M=M-1', //ic+4
// set M=-1 (TRUE), in case they are equal
// *SP=-1 = true
]);
default:
# code...
break;
}
$this->write([
// And then write the result back to M
"M=D",
// Now we write our current A to SP
"A=A+1",
"D=A",
"@SP",
"M=D",
"// ==== $command ===="
'@SP',
'M=M-1'
]);
}
private function write(Array $lines) {
foreach ($lines as $line) {
if (substr($line, 0, 2) !== "//") {
$this->ic += 1;
}
fwrite($this->file, "$line\n");
}
}
@ -131,10 +144,8 @@ class CodeWriter {
// Write D to SP
"M=D",
// Bump Stack Pointer
"A=A+1",
"D=A",
"@SP",
"M=D",
"M=M+1",
"// end push $segment $index"
]);
break;
@ -159,10 +170,6 @@ class CodeWriter {
break;
}
}
function close() {
throw new \Exception("Not yet Implemented");
}
}

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